1. Field of the Invention
The relates to a hydrorefining catalyst containing suphides of ruthenium and of at least one other metal and a process for hydrorefining hydrocarbon feedstocks using the said catalyst.
2. Background Art
Petroleum and petroleum fractions obtained by distillation or oil processing are complex mixtures in which, besides hydrocarbons, there are compounds containing heteroatoms, such as sulphur, nitrogen and oxygen. Heavy feedstocks, the use of which is becoming increasingly widespread, contain large quantities of heteroatomic compounds. These heavy feedstocks consist, for example, of heavy crudes, of bituminous schists or of heavy residues from oil refineries.
Heteroatomic compounds are impurities which are detrimental to the good quality of petroleum products. They are responsible especially for problems related to pollution, corrosion, odour and stability. Sulphur and nitrogen compounds can also poison the usual catalysts in the refining processes.
It is therefore important to remove them in the course of refining. This generally involves a treatment with hydrogen in the presence of a catalyst which promotes the rupture of carbon-heteroatom bonds. This treatment is known as hydrorefining.
The main hydrorefining reactions are desulphurisation, denitrogenation and the saturation of aromatic compounds. Desulphurisation consists in converting the sulphur present in the organic compounds into hydrogen sulphide. Denitrogenation consists in converting the nitrogen in the organic compounds into ammonia.
A considerable research effort has been deployed to find efficient hydrorefining catalysts which resist deactivation by heteroatoms.
The most commonly employed hydrorefining catalysts are bimetallic catalysts based on nickel, molybdenum, tungsten or cobalt. These metals are deposited on supports by impregnation with the aid of their water-soluble salts, and are then converted into sulphides. The supports are generally based on refractory oxides such as alumina or silica-aluminas.
Among the bimetallic hydrorefining catalysts we can mention the catalysts based on nickel/molybdenum and cobalt/molybdenum. The Procatalyse catalyst HR 346 contains nickel/molybdenum on alumina, and the HR 348 nickel/molybdenum on doped alumina.
It is known that these commercial catalysts result in quite easy conversion of quinolines to alkylanilines, but the latter, although readily denitrogenated when pure, are only very slightly converted in the presence of quinolines. An accumulation of alkylanilines therefore takes place in the feedstocks, and this at present constitutes one of the chief limitations of the denitrogenation efficiencies obtained in refining.